[Arran]

It's unlikely that a set this old would have used oil caps, more then likely they were large paper caps, stuffed in the bottom of the filter block. Since this set was based on an American Bosch model 28, which was a reworked Radiola 17 or 18, this was haw it would have been constructed, and they are actually fairly easily removed in those two sets, the hardest part is unbending the metal tabs that hold the can in place. These set were straight TRF, no Neutrodyne, Neutrodynes use an extra winding on each RF coil for inverse feedback, the Radiola 17 and 18 used neutralizing condensers.
Regards
Arran